The present invention relates to a sensor apparatus, and more particularly to a sensor apparatus that is positioned in an air duct system to measure airflow by sensing a pressure differential.
Air duct systems are used for heating, cooling, or ventilating controlled spaces by directing an airflow from a source (e.g., furnace, air conditioner, cold or hot air return, etc.) via air ducts to the controlled spaces. In some air duct systems, the airflow is balanced by measuring the airflow in the air duct with an airflow sensing system that is installed in one or more locations in the air duct. In other air duct systems, a portable sensing system can be used to balance the airflow. Often, portable sensing systems include a hood or box that captures the airflow and directs the airflow across a sensing apparatus to measure the airflow.
Generally, an airflow sensing system measures the total pressure and the static pressure of the airflow in the duct. The total and static pressure measurements are used to determine the velocity pressure of the airflow. In some existing air duct systems, the airflow sensing system includes a total pressure sensing tube that measures a total pressure of the airflow, and a static pressure sensing tube that measures the airflow at a stagnation point. The total pressure sensing tube and the static pressure sensing tube are in communication with a controller that determines the airflow based on the measured total and static pressures.
Some existing airflow sensing systems include two or more pressure sensing tubes that are oriented perpendicular to each other (e.g., in a cross-shape). The two pressure sensing tubes are used to measure the total pressure of the airflow. These sensing tubes include one or more airflow ports facing the airflow, and one pressure averaging portion that is positioned at the center or junction of the two pressure sensing tubes (i.e., the intersection of the two sensing tubes). These existing sensing tubes measure the total pressure of the airflow via the airflow ports, and the total pressure of the airflow from each of the holes is averaged at the center pressure averaging portion.
These airflow sensing systems commonly include a static pressure sensing tube that is positioned away from the airflow to sense a static pressure. The total pressure and the static pressure are communicated to the controller, which then calculates the airflow.